The present invention relates to a load control system.
In a typical load control system, one load is controlled by one control device, except for a special load which is controlled by a plurality of control devices, for example, a power window motor which needs reversing.
In order to control the lighting of a plurality of lamps, for example, a control device Tr such as a relay and a power transistor is installed between each of the lamps LP1-LPn and a power supply Vcc or between each of the lamps LP1-LPn and the ground G as shown in FIG. 16. Then the lamps LP1-LPn are lighted by causing the control devices Tr to conduct by means of switches.
However, there still exists a problem arising from an increase in cost because the control devices equal in number to the loads are required.
Since wiring is increasingly needed corresponding to the number of control devices increases, the wiring work becomes complicated. In the case of a substrate, the pattern also tends to become complicated. This results in developing the problem of raising the aforementioned cost further.
According to the conventional arrangement, since the conductive wires equal in number to the loads desired to be driven are required in such a load driving system and when this system is employed for driving a number of loads such as lamps and door locks in automobiles, for example, wire harness such as the conductive wires tend to become multiplied and complicated.
In order to decrease the number of conductive wires such as wire harness, recently, as shown in FIG. 17, the switches SW1, SW2, SW3 are connected to the corresponding signal input terminals of an encoding microcomputer 4; the power supply terminals of the loads L1, L2, L3 are connected to the corresponding output terminals of a decoding microcomputer 5; and further a multiplex communication cable 6 is used for connecting these microcomputers 4, 5. With this arrangement, the code generated in the encoding microcomputer 4 on the basis of the switches SWI, SW2, SW3 that have been actuated is transmitted to the decoding microcomputer 5 via the multiplex communication cable 6, and the decoding microcomputer 5 drives the desired loads L1, L2, L3 according to the code, so that the number of conductive wires is greatly decreased.
Notwithstanding, the load driving system like this becomes costly because it requires the encoding and decoding microcomputers 4, 5.